POS0361 COMPREHENSIVE TRANSCRIPTOMIC CHARACTERIZATION REVEALS CORE GENES AND MODULES ASSOCIATED WITH SEX-DEPENDENT MOLECULAR PAIN MECHANISMS IN OSTEOARTHRITIS
Authors: Z. Wang, V. Batchelor, J. Miotla-Zarebska, B. Gerritsen, N. Eijkelkamp, T. Vincent, C. Svensson
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Female sex is identified as a key nonmodifiable risk factor in the development of OA, particularly after the age of 55. Additionally, women appear to have a lower threshold for pain and present with more chronic pain conditions than men. Our previous studies demonstrated that female mice develop pain at the same time as male mice despite having reduced levels of joint damage, indicating the existence of sex-dependent mechanisms for the induction of pain. In non-arthritis murine pain models, different immune cells in the dorsal root ganglia (DRG) appear to contribute to sex-dependent differences in sensitization. Furthermore, we have recently uncovered cellular and molecular differences between immune cells and inflammatory profiles in the DRGs and joints of male and female mice with collagen antibody-induced arthritis. <h3>Objectives</h3> Search for putative pain pathways and associated temporal patterns in male and female mice subjected to surgically induced OA. <h3>Methods</h3> C57BL/6 male and female mice (10-week-old, n=5 per group, i.e., surgery, sex, and timepoint) were randomized subjected to either sham surgery or partial meniscectomy (PMX). Static weight bearing measurements were performed using a Linton Incapacitance Tester. Mice underwent a 2-week acclimatization post-surgery, followed by weekly measurement between week 5 to 12. L3-L4 DRGs were harvested for RNA sequencing at week 6, 10 and 12 post-surgery. The Weighted Gene Co-expression Network Analysis (WGCNA) package in R was used to construct a signed co-expression network from the expression data. <h3>Results</h3> Considering all groups, a tendency to pain-related behavior was observed at week 10 post-surgery, and a statistically significant difference in weight bearing found at week 12 when the PMX group was compared with sham group. We performed WGCNA to identify modules that were related to surgery and sex using 6-, 10-, and 12-week samples, respectively. For the 6-week network, 14 modules were identified. Only associations with sex were observed, with 3 modules positively related with male and 1 module positively related with female. For the 10-week network, 14 modules were identified. 6 modules were related by single trait, 3 of which were positively related with male, 2 of which were positively related with PMX, and 1 of which weas negatively related with PMX. In addition, 1 module was related with both surgery and sex, whereby it was negatively related with PMX and positively with being female. For the 12-week network, 19 modules were identified. Most significant associations were observed only with PMX, where 5 modules showed positive associations and 3 modules showed negative associations. Furthermore, greenyellow module was related with both surgery and sex, positively related with PMX and being female. As a result, this module was chosen to investigate further. According to the threshold (MM &gt; 0.8 and GS &gt; 0.2), 102 candidate hub genes were obtained in this module. When PPI analysis was performed, 14 candidate hub genes (top 5%, ranked by the MCC scoring method) were obtained. In total, 9 overlapping genes (Npy, Tac1, Calca, Gap43, Bdnf, Shc1, Ngfr, Casp3 and Jun) were identified as hub genes. The enriched biological process was 'neurotrophin TRK receptor signaling pathway'. And the enriched KEGG pathway were 'neurotrophin signaling pathway' and 'MAPK signaling pathway'. <h3>Conclusion</h3> This study reveals sex, disease and time-dependent changes in the DRG transcriptome during the development of painful OA. Importantly, our findings highlight a distinct TrkA and neurotrophin signaling signature that is evident at 12 weeks post-surgery only in OA-induced pain-related behaviors in female mice. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.